Inter-shaft bearing arrangement

ABSTRACT

A sleeve is provided for supplying lubricant to an inter-shaft bearing mounted between co-axially mounted inner and outer shafts of a gas turbine engine. The sleeve has a sleeve annular outer surface and a sleeve annular inner surface. At least one lubricant supply connecting member extends from the sleeve outer surface for connection to a lubricant supply. At least one sleeve channel fluidly links the sleeve annular inner surface to the lubricant supply connecting member.

TECHNICAL FIELD

The application relates generally to gas turbine engines and, moreparticularly, to bearings arrangements for co-axially mounted shafts.

BACKGROUND OF THE ART

Co-axially mounted shafts of gas turbine engines are known to includebearing assemblies in between. One such bearing assembly, known asdamped bearing, comprises a thin (in the order of a few thousandths ofan inch) annular area between a bearing race and a shaft, known as adamping annulus, which, when filled with lubricant, allows the bearingassembly to compensate for slight misalignments and to absorb smallshaft vibrations during operation. Getting lubricant to the dampingannulus, with the requisite fluid characteristics (such as pressure), isan ongoing challenge for gas turbine engine designers.

There is an ongoing need for novel inter-shaft damped bearingarrangements, more specifically for providing lubricant to the dampingannulus area of such bearing arrangement.

SUMMARY

In one aspect, there is provided a gas turbine engine comprising: aninter-shaft bearing mounted radially between an inner shaft and a hollowouter shaft, the inner shaft being co-axially mounted inside the hollowouter shaft, the hollow outer shaft comprising a through-shaftpassageway extending from an inner surface to an outer surface of suchhollow outer shaft, a damping annulus located radially between an outerrace of the inter-shaft bearing and an inner surface of the outer shaft,a sleeve, positioned circumferentially around the hollow outer shaft,and a lubricant buffer annulus located radially between the outersurface of the outer shaft and the sleeve; wherein the through-shaftpassageway fluidly links the damping annulus with the lubricant bufferannulus and the sleeve defines a lubricant passage fluidly linking thelubricant buffer annulus to a lubricant supply.

In another aspect, there is provided a sleeve for supplying lubricant toan inter-shaft bearing mounted between a co-axially mounted inner andouter shaft of a gas turbine engine, wherein the sleeve comprises: asleeve annular outer surface, a sleeve annular inner surface, at leastone lubricant supply connecting member extending from the sleeve annularouter surface and adapted to be connected to a lubricant supply, and atleast one sleeve channel fluidly linking the sleeve annular innersurface to the at least one lubricant supply connecting member.

In a further aspect, there is provided a method for providing oil to aninter-shaft bearing, mounted between an inner shaft co-axially mountedwithin a hollow outer shaft of a gas turbine engine, the inter-shaftbearing comprising a damping annulus located between an outer race ofthe inter-shaft bearing and an inner surface of the hollow outer shaft,the method comprising: providing an opening in the hollow outer shaftfor fluidly linking the damping annulus with an outer surface of theouter shaft, and providing a static sleeve around the outer shaft forfluidly linking the outer surface of the outer shaft with a pressurisedoil supply.

Further details of these and other aspects of the subject matter of thisapplication will be apparent from the detailed description and drawingsincluded below.

DESCRIPTION OF THE DRAWINGS

Reference is now made to the accompanying figures in which:

FIG. 1 is a schematic cross-sectional view of a gas turbine engine;

FIG. 2 is a side sectional view of an inter-shaft bearing arrangementpursuant to an embodiment,

FIG. 3 is a front sectional view of an inter-shaft bearing arrangementpursuant to an embodiment;

FIG. 4 is an isometric view of a sleeve pursuant to an embodiment; and

FIG. 5 is a side sectional view of an outer race of an inter-shaftbearing pursuant to an embodiment.

DETAILED DESCRIPTION

FIG. 1 illustrates an example of a turbofan gas turbine engine 1generally comprising a housing or nacelle 10; a low pressure spoolassembly 12 including a fan 11, a low pressure compressor 13 and a lowpressure turbine 15; a high pressure spool assembly 14 including a highpressure compressor 17, and a high pressure turbine 19; and a combustor16 including fuel injecting means 21. The low pressure spool assembly 12and high pressure spool assembly 14 are concentrically mounted aboutengine centerline A; more specifically (as described and shown in moredetails below), engine 1 comprises 2 shafts co-axially (around enginecentreline A) mounted within one another and a bearing assembly, knownas an inter-shaft bearing assembly, mounted in between. Throughout thisdescription, centerline A will be used to locate terms with inner andouter qualifiers; for example, inner and outer surface of an item willrefer to the radially closer surface (inner) and the radially farthersurface (outer) in relation to such centerline A.

As shown in FIGS. 2-3, inner shaft 30 and hollow outer shaft 50 areco-axially mounted within one another and rotate around centreline Aduring operation of engine 1. An inter-shaft bearing assembly 40 ismounted radially between inner shaft 30 and outer shaft 50. In thecurrent embodiment, inter-shaft bearing assembly 40 is an inner diameter(ID) pilot type bearing, meaning that the primary bearing attachmentoccurs on its inner diameter (with its outer diameter being allowed somefreedom of movement). More specifically, inner race 41 of inter-shaftbearing assembly 40 is secured, through a tight fit or other suitablemeans of attachment, to inner shaft 30, more specifically to inner shaftradially outer surface 33, so that, during operation, inner race 41rotates with inner shaft 30. Outer race 43 is allowed some freedom ofmovement with respect to outer shaft radially inner surface 51, morespecifically radial freedom of movement. In the current embodiment,outer race 43's attachment with respect to outer shaft radially innersurface 51 is accomplished through a male-female pin extensionattachment arrangement 48, which allows outer race 43 some radial but nosignificant axial or circumferential freedom of movement with respectouter shaft 50; but any other type of suitable attachment, besidesmale-female pin extension attachment arrangement 48, is possible.

Inter-shaft bearing assembly 40 is a rolling-element bearing, but otherbearing types, which benefit from lubricant contribution duringoperation, are possible pursuant. In the current embodiment, inter-shaftbearing assembly 40 is a roller bearing, meaning that the rollingelements placed between inner race 41 and outer race 43 are cylindricalrollers 42 (only a few of which are shown in FIG. 3 for ease ofdisplay). Other types of rolling-element bearing types, such as ballbearings (where the rolling elements placed between inner race 41 andouter race 43 are spherical balls), are possible.

Inter-shaft bearing assembly 40 is a damped bearing, meaning that thereis a thin (in the order of a few thousandths of an inch) annular 45between outer race 43 and outer shaft radially outer surface 53, suchannular 45 being known as a damping annulus 45 because, when filled withlubricant during operation, it allows inter-shaft bearing assembly 40 tocompensate for slight misalignments and to absorb small shaftvibrations.

Outer shaft 50 comprises a through-shaft passageway, in the currentembodiment at least one hole 57 extending between outer shaft radiallyinner surface 51 and outer shaft radially outer surface 53, therebyfluidly linking damping annulus area 45 with outer shaft radially outersurface 53. It should be noted that the current embodiment discloses aplurality of holes 57 (more clearly shown in FIG. 3), as outer shaft 50may have any suitable number of holes 57 as necessary to meet therelevant needs (to be described in more details below). Whereas thecurrent embodiment shows holes 57 as substantially radial (i.e. thehole's centerline passes through centreline A), holes 57 may be angled(i.e. the hole's centerline does not pass through centreline A).Furthermore, holes 57 can be circumferentially equidistant from oneanother or not. Finally, whereas the current embodiment shows holes 57as being axially aligned (i.e. are located on the same axial plane),holes 57 which are not so aligned, such as with a sieve-typeconfiguration, is possible.

A sleeve 60 (shown by itself in FIG. 4,) is positioned around outershaft 50. Sleeve 60 is static, meaning that it does not rotate duringoperation. Sleeve 60 comprises an annular outer surface 63 and anannular inner surface 61. Sleeve 60 comprises a lubricant passagefluidly linked to a lubricant supply, in the current embodiment a sleevechannel 67, fluidly linked to a pressurised oil supply 70 (shownschematically in FIG. 2-3 by a double-arrow), extending through sleeve60. Sleeve channel 67 is consequently fluidly linking pressurised oilsupply 70 with an annular space between annular inner surface 61 andouter shaft radially outer surface 53, hereinafter defined as lubricantbuffer annulus area 55. Sleeve channel 67 fluidly links pressurised oilsupply 70 with lubricant buffer annulus area 55, via a lubricant supplyconnecting member 69 positioned on sleeve channel 67's outer extremity.Sleeve channel 67 and lubricant supply connecting member 69 aredimensioned to provide the necessary amount of lubricant (in the currentembodiment pressurised oil) from the lubricant supply (in the currentembodiment pressurised oil supply 70) to the lubricant buffer annulusarea 55, to meet the relevant needs (as described below).

During operation, there is a need to provide lubricant, in the currentembodiment oil, to damping annulus area 45 of inter-shaft bearingassembly 40. Such oil is provided to damping annulus area 45 from the atleast one hole 57 which, in turn, originates from lubricant bufferannulus area 55 which, in turn, originates from the at least one sleevechannel 67 which, in turn, originates from pressurised oil supply 70.Oil supply 70 is pressurised because oil that is to be provided todamping annulus area 45 needs to have the requisite fluidcharacteristics (more specifically pressure characteristics) to addressthe issues, such as centrifugal force issues, that exist in the dampingannulus area 45. It is however possible, to have an unpressurisedlubricant supply connected to lubricant supply connecting member 69, aslong as the other elements of this inter-shaft bearing arrangementcontribute to ensure that the requisite fluid characteristics of thelubricant provided to damping annulus area 45 are met. For example, thequantity and characteristics (such as the angle of the hole's centerlineand the hole's shape) of holes 57 may be such that, when rotating duringoperation, the requisite fluid characteristics of the lubricant providedto damping annulus area 45 is achieved. Characteristics of sleeve 60will also factor into meeting the requisite fluid characteristics of thelubricant provided to damping annulus area 45. Indeed, although thecurrent embodiment discloses 2 sleeve channels 67, sleeve 60 may have 1or any suitable number of sleeve channels as necessary to meet therelevant needs. Furthermore, whereas the current embodiment shows sleevechannels 67 as substantially radial (i.e. the hole's centerline passesthrough centreline A), sleeve channels 67 may be angled (i.e. the hole'scenterline does not pass through centreline A). Still furthermore,whereas the current embodiment shows sleeve channels 67 as beingcircumferentially equidistant from one another, sleeve channels 67 whichdo not have such equidistant characteristic is possible. Finally,whereas the current embodiment shows sleeve channels 67 as being axiallyaligned (i.e. are located on the same axial plane), sleeve channels 67which are not so aligned is possible.

Sleeve channel 67 fluidly links the lubricant supply with lubricantbuffer annulus area 55. In circumstances where lubricant buffer annulusarea 55 is not of a sufficient thickness to meet the requisite fluidcharacteristics of the lubricant provided to damping annulus area 45, alubricant reserve area channel 64 can be added between sleeve annularinner surface 61 and sleeve channel 67. Lubricant reserve area channel64 increases the area from which holes 57 can draw its lubricant andfluidly links damping annulus area 45 with the lubricant supply. Asshown in FIG. 4, lubricant reserve area channel 64 may extendcircumferentially around the whole sleeve annular inner surface 61.However, as shown in FIG. 3, lubricant reserve area channel 64 may onlyextend partially circumferentially around sleeve annular inner surface61. Finally, whereas the current embodiment shows a single lubricantreserve area channel 64, it is possible to have (axially) side-by-sidelubricant reserve area channels 64; in this latter case, sleeve channels67 would have to be dimensioned and positioned to fluidly linkpressurised oil supply 70 with each such lubricant reserve area channel64.

As shown in FIG. 5, inter-shaft bearing assembly 40, more specificallyouter race 43, may further include at least one bearing annular gasket46 for reducing the amount of lubricant axially leaking from dampingannulus area 45. In the current embodiment, a bearing annular gasket 46is positioned at each axial extremity of outer race 43 so as to preventlubricant axially leaking from both axial ends of damping annulus area45. Annular gaskets 46 may be of the piston or o-ring variety.

Similarly, although not shown in any of the Figures, sleeve 60 may alsoinclude annular gaskets on its annular inner surface 61 for reducing theamount of lubricant axially leaking from lubricant buffer annulus area55 and/or for reducing the amount of lubricant leaking from lubricantreserve area channel 64.

The above description is meant to be exemplary only, and one skilled inthe art will recognize that changes may be made to the embodimentsdescribed without departing from the scope of the present disclosure.Still other modifications which fall within the scope of the presentdisclosure will be apparent to those skilled in the art, in light of areview of this disclosure, and such modifications are intended to fallwithin the appended claims.

1. A gas turbine engine comprising: an inter-shaft bearing mountedradially between an inner shaft and a hollow outer shaft, the innershaft being co-axially mounted inside the hollow outer shaft, the hollowouter shaft comprising a through-shaft passageway extending from aninner surface to an outer surface of such hollow outer shaft, a dampingannulus located radially between an outer race of the inter-shaftbearing and an inner surface of the outer shaft, a sleeve, positionedcircumferentially around the hollow outer shaft, and a lubricant bufferannulus located radially between the outer surface of the outer shaftand the sleeve; wherein the through-shaft passageway fluidly links thedamping annulus with the lubricant buffer annulus and the sleeve definesa lubricant passage fluidly linking the lubricant buffer annulus to alubricant supply.
 2. The gas turbine engine as defined in claim 1,wherein the lubricant passage comprises a lubricant reserve channelextending radially outwardly from an annular inner surface of thesleeve.
 3. The gas turbine engine as defined in claim 2, wherein thelubricant reserve channel extends around the full circumference of thesleeve annular inner surface.
 4. The gas turbine engine as defined inclaim 3, wherein the lubricant supply is a pressurised oil supply. 5.The gas turbine engine as defined in claim 1, wherein the through-shaftpassageway comprises at least one hole extending from the inner surfaceto the outer surface of the hollow outer shaft.
 6. The gas turbineengine as defined in claim 5, wherein the lubricant supply is apressurised oil supply.
 7. The gas turbine engine as defined in claim 5,wherein the at least one hole is a substantially radial hole.
 8. The gasturbine engine as defined in claim 1, wherein the lubricant passagecomprises a sleeve channel fluidly connected to a lubricant supplyconnecting member, wherein the sleeve channel is fluidly linked to thelubricant buffer annulus and the lubricant supply connecting member isfluidly linked to the lubricant supply.
 9. The gas turbine engine asdefined in claim 2, wherein the lubricant passage comprises a sleevechannel fluidly connected to a lubricant supply connecting member,wherein the sleeve channel is fluidly linked to the lubricant reservechannel and the lubricant supply connecting member is fluidly linked tothe lubricant supply.
 10. The gas turbine engine as defined in claim 1,wherein the lubricant passage comprises at least 2 sets of a sleevechannel fluidly connected to a lubricant supply connecting member,wherein each sleeve channel is fluidly linked to the lubricant bufferannulus and each lubricant supply connecting member is fluidly linked tothe lubricant supply, each set of sleeve channel fluidly connected to alubricant supply connecting member being positioned substantiallycircumferentially equidistant from one another.
 11. The gas turbineengine as defined in claim 2, wherein the lubricant passage comprises atleast 2 sets of a sleeve channel fluidly connected to a lubricant supplyconnecting member, wherein each sleeve channel is fluidly linked to thelubricant reserve channel and each lubricant supply connecting member isfluidly linked to the lubricant supply, each set of sleeve channelfluidly connected to a lubricant supply connecting member beingpositioned substantially circumferentially equidistant from one another.12. The gas turbine engine as defined in claim 1, wherein theinter-shaft bearing is fixed to the inner shaft.
 13. The gas turbineengine as defined in claim 1, further comprising an attachment betweenthe outer race of the inter-shaft bearing and the radially inner surfaceof the outer shaft, the attachment allowing radial freedom of movement.14. The gas turbine engine as defined in claim 1, wherein the outer raceof the inter-shaft bearing comprises at least one annular gasket.
 15. Asleeve for supplying lubricant to an inter-shaft bearing mounted betweena co-axially mounted inner and outer shaft of a gas turbine engine,wherein the sleeve comprises: a sleeve annular outer surface, a sleeveannular inner surface, at least one lubricant supply connecting memberextending from the sleeve annular outer surface and adapted to beconnected to a lubricant supply, and at least one sleeve channel fluidlylinking the sleeve annular inner surface to the at least one lubricantsupply connecting member.
 16. The sleeve as defined in claim 15, furthercomprising at least one lubricant reserve channel extending radiallyoutwardly from, and at least partially around a full circumference of,the sleeve annular inner surface, wherein the at least one sleevechannel fluidly links the at least one lubricant reserve channel to theat least one connecting member.
 17. The sleeve as defined in claim 16,wherein the at least one lubricant reserve channel extends around thefull circumference of the sleeve annular inner surface.
 18. A method forproviding oil to an inter-shaft bearing, mounted between an inner shaftco-axially mounted within a hollow outer shaft of a gas turbine engine,the inter-shaft bearing comprising a damping annulus located between anouter race of the inter-shaft bearing and an inner surface of the hollowouter shaft, the method comprising: providing an opening in the hollowouter shaft for fluidly linking the damping annulus with an outersurface of the outer shaft, and providing a static sleeve around theouter shaft for fluidly linking the outer surface of the outer shaftwith a pressurised oil supply.
 19. A method for providing lubricant toan inter-shaft bearing as defined in claim 18, further comprisingproviding a lubricant reserve channel within the sleeve for fluidlylinking the outer surface of the outer shaft to the pressurised oilsupply.
 20. A method for providing lubricant to an inter-shaft bearingas defined in claim 19, further comprising providing a lubricant supplyconnecting member, extending from the sleeve, for fluidly linking thelubricant reserve channel to the pressurised oil supply.